TY - JOUR

T1 - Nusselt numbers from numerical investigations of turbulent flow in highly eccentric horizontal annuli

AU - Zimmermann, Conrad

AU - Lemcke, Felix J.

AU - Kabelac, Stephan

PY - 2019/12

Y1 - 2019/12

N2 - Fluid flow and heat transfer in annuli appear in various technical applications. One of these are actively cooled underground cables, which are a solution for high-voltage transmission grids that face overloads due to a growing capacity of renewable sources. The cooling of these systems depends on precise prediction of heat transfer of a highly eccentric annulus in a way that has not been subject to any known literature or former research. This article presents Nusselt numbers obtained from CFD calculations for turbulent flow (20,000 < Re < 150,000) in highly eccentric annuli (dimensionless eccentricity e up to 0.95). The mesh and turbulence models are validated with well-known correlations from literature, which show very good accordance. Nusselt numbers show a high dependency on the eccentricity. They strongly decrease for e > 0.5 and drop to a third and less for e = 0.95 in comparison to concentric annuli. This has significant impact on the assurance of safe operation in actively cooled cable systems. Results also indicate a change of flow characteristics from laminar to turbulent depending on the eccentricity that should be considered in order to improve heat transfer.

AB - Fluid flow and heat transfer in annuli appear in various technical applications. One of these are actively cooled underground cables, which are a solution for high-voltage transmission grids that face overloads due to a growing capacity of renewable sources. The cooling of these systems depends on precise prediction of heat transfer of a highly eccentric annulus in a way that has not been subject to any known literature or former research. This article presents Nusselt numbers obtained from CFD calculations for turbulent flow (20,000 < Re < 150,000) in highly eccentric annuli (dimensionless eccentricity e up to 0.95). The mesh and turbulence models are validated with well-known correlations from literature, which show very good accordance. Nusselt numbers show a high dependency on the eccentricity. They strongly decrease for e > 0.5 and drop to a third and less for e = 0.95 in comparison to concentric annuli. This has significant impact on the assurance of safe operation in actively cooled cable systems. Results also indicate a change of flow characteristics from laminar to turbulent depending on the eccentricity that should be considered in order to improve heat transfer.

KW - Annulus

KW - Cooled cable

KW - Eccentric

KW - Forced convection

KW - Heat transfer

KW - Nusselt number

UR - http://www.scopus.com/inward/record.url?scp=85074126753&partnerID=8YFLogxK

U2 - 10.1016/j.icheatmasstransfer.2019.104344

DO - 10.1016/j.icheatmasstransfer.2019.104344

M3 - Article

AN - SCOPUS:85074126753

VL - 109

JO - International Communications in Heat and Mass Transfer

JF - International Communications in Heat and Mass Transfer

SN - 0735-1933

M1 - 104344

ER -